The House voted 256-40 to approve the change and send the bill to the Senate.

At least 40 other states and the federal government treat the teens as juveniles. New Hampshire lowered its minimum age for adult suspects from 18 to 17 in 1996, and attempts to raise it have failed over the years.

Supporters argue the teens are still of an age when they can be rehabilitated if sent to the state reformatory instead of prison.

Opponents argued the teens should be held accountable as adults.

"Walking among us are monsters and those monsters come in all ages," objected Rep. William O'Brien, who cited the murder of a mother and injury of her teenage daughter in his hometown of Mont Vernon.

Steven Spader was a month shy of turning 18 when he killed the woman, Kimberly Cates, in 2009. Co-defendant Christopher Gribble and Spader are both serving life sentences. Three others in prison accepted a plea deal and testified against Spader.

But Rep. Dan Eaton, D-Stoddard, pointed out that prosecutors would retain the right to ask a judge to certify 17-year-olds as an adult for major crimes. Eaton said the people O'Brien referred to as "monsters" would be treated as adults.

Most of the 17-year-old suspects are accused of lesser crimes, not murder, said Rep. David Huot, D-Laconia.

"Those offenses need to be dealt with in a different way," he said.

Raising the age would mean that crimes committed by 17-year-olds no longer would become part of an adult criminal record.

New Hampshire lowered the age in 1996 in response to arguments that criminals in Massachusetts were sending 17-year-olds into New Hampshire carrying drugs. If the Massachusetts teens were caught in New Hampshire, they were put through the juvenile system.

In the past decade, the national trend has been to increase the age and send 17-year-olds through the juvenile system, according to a report by the National Conference of State Legislatures.

Massachusetts is among the states to raise its age recently. Gov. Deval Patrick signed a law in September raising the age to 18. Massachusetts' law change removes the original motivating force behind New Hampshire's 1996 law.

The change would be effective July 1, 2015, to give lawmakers time to account for any costs associated with the population shift from the prison to reformatory.

The House Finance Committee estimated the cost could be $2.4 million in the next budget, but added the estimate could be high since caseloads have been declining. The committee said the change could save counties millions of dollars for complying with the federal Prison Rape Elimination Act requirements that 17-year-olds be separated from older prisoners.